Grain of discomfort (4)
I believe the answer is:
corn
This clue might be a double definition.
'grain' is the first definition.
(I know that corn is a type of kernel)
'discomfort' is the second definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'of' is the link.
Can you help me to learn more?
(Other definitions for corn that I've seen before include "Cereal crop; callus" , "Painful affliction" , "Cereal grass" , "Type of cereal" , "Crop - growth" .)